Forced circulation boiler



Oct. 21, 1952 J. w. HOOD FORCED CIRCULATION BOILER Filed April 1. 1947 78 Y 56 co/vaM/z5/2 INVENTOR. 77185 [1/ Hood proximately 50% at circuit exit, to thus provide a substantial factor of safety to reduce tube failure due to over-concentration of solids or superheat conditions resulting from heat unbalance between circuits, over-firing due to heat storage, over-firing due to subnormal pressure, etc.

It is a further object of this invention to provide a forced circulation boiler design to Provide greater stability due to its increased water storage.

It is a further object of this invention to provide a forced circulation boiler having two or more forced circulation sections arranged in series to generate and discharge steam into a steam drum or separator, together with means for automatically controlling the operation of said sections.

It is a further object of this invention to provide a forced circulation boiler embodying one or more natural circulation sections and a continuous blow-down to take the place of the spillover apparatus heretofore employed in once-thru boilers.

This invention embodies other novel features,

details'of construction and arrangement of parts which are hereinafter set forth in the specification and claims and illustrated in the accompanying drawing wherein:

Fig. 1 is a schematic view illustrating a forced circulation boiler embodying features of this invention.

Fig. 2 is a wire diagram illustrating the means employed to vary the flow of steam from the primary separator to the secondary separator responsive to variations in water level within said primary'separator.

Referring now to the drawing for a better understanding of this invention, the forced circulation boiler is shown as comprising a pump 6 for forcing feed water under pressure through a boiler inlet conduit I into a lower header 8 and thence upwardly through a group of tubes 3 employed as a primary heating section II. Steam and'water are directed from the primary heating section I I into a top header I0 and thence into a primary separator I2.

A steam conduit I3 leads from the top of the primary separator I 2 to an augment nozzle or jet I 4 interposed in a natural circulation section generally indicated at I6. Water within the primary separator I2 is directed downwardly through a conduit I'I into a lower header I8 and thence upwardly through a group of tubes I9 comprisinga secondary heating section 2I. water leaving the secondary heating section 2I are directed into a top header 20 and thence into a secondary separator 22. Steam within the secondary separator 22 may be directed from line 23 either through an outlet line 25 to the point of use, or to a superheater 24 and thence to a point of use through a conduit 26.

Thus, thenatural circulation section I6 comprises headers 28 and 3|, a series of heating tubes 29, and includes an inlet line 21 and an outlet line 33. The plurality of tubes 29 lead from the lower header 28 to the upper header 3I to serve as an auxiliary heating section 32 which is designed and arranged to absorb approximately 25% of the total heat absorbed by the boiler heating sections II, 2I and I6. The conduit 33 leads from the upper header 3I to the secondary separator 22, and therefore comprises an inlet to the separator from said header 3I.

In the event the temperature of the Water leav- Steam and ing the primary separator I2 through the conduit I1 is too high, it may flash into steam. It is, therefore, desirable to provide an auxiliary feed water inlet 34 to direct a supply of relatively cooler water from an economizer 36 to the conduit I I.

A return conduit 3'! leads from the primary separator I2 downwardly to the lower header 8; and a return conduit 38 leads downwardly from the secondary separator 22. to the lower header I8. Check valves 39 and 4! are interposed in the return conduits 31 and 33, respectively, to permit a flow of water from the separators I2 and 22 to their respective lower headers 8 and I8 when the head between the separators and their respective headers becomes greater than the pressure drop through their respective heating sections I I and 2 I. It will thus be noted that the boiler unit could be operated with natural circulation under very light loads. A continuous blow-down 42 comprising a conduit 43 and a blow-oil valve 44 is provided for the secondary separator 22 to regulate a concentration of solids therein. The continuous blow-down 42 is also useful in placing the boiler in operation.

The water level within the primary separator I2 is regulated by means of a pair of electrodes I04 and I06, electrode I04 being connected in a circuit I01 leading to a switch terminal I08, thence through a relay I09 and secondary winding III of a transformer II 2 to ground. The electrode I06 is connected in a holding circuit II3 leading through a switch 4, relay I09 and secondary winding III to ground. The primary winding I I6 of the transformer is connected to a suitable source of current. The supply of steam passing from primary separator I2 to the secondary separator 22 through the conduit I3 is controlled by a valve I I1 which is operated by means of a solenoid II8 connected to a suitable source of current through a circuit H9. A switch I21 is interposed in the circuit II9 to make or break the circuit leading to the solenoid II8 when actuated by the relay I 09.

In the operation of this electric control means for regulating the water level within the primary separator I2, a surface contact between the water and the electrode I04 acts to energize the relay I03 to complete the holding circuit through the switch H4, and to open the switch I2I in the circuit leading to the solenoid I I8. De-energization of the solenoid II 3 acts to move the valve II I to a partially closed position to provide a restricted passage for the passage of steam through the conduit I3, and thus increase the pressure drop between the primary and secondary separators and thus causing an increased flow of water from the primary separator I2 downwardly through the conduit I'I.

When the water level within the primary separator I2 falls below the end of the electrode I06, the holding circuit I I3 to the relay I09 is broken, thereby opening the switch H4 and closing the switch I2 I. The closing of the switch I2I causes the solenoid II8 to open the valve II! to a full open position, if desired, to permit a substantially unrestricted flow of steam from the primary separator I2 through the conduit I3 to the secondary separator 22. While a rather simple form of control has been shown and described for operating the valve II'I between a full open position and partly open position, it is obvious that other forms of control means could be provided whereby the valve I I! could be adjusted for set- 5;; tingsiintermediateamlli openzpositiorrzandi-a re 1 stQ-ted partly one position; 3 1 th'e operation' I'of' the lforced scirculation boiler of the type -shown and udescribemto gene ert'e; or example, 20,000- pounds :of 'zsteam, per

'hou1 =at '1-500 p. s. i.i the;secondary:iseparatori-ll;

with 5.0%5-stea2rn quality atithe eXiblGfIbOth; forced ection's I -l and 2 hand-embodying aanrecon-a omi-z'er 'for heatingthelfeediwateritojflflfofir an proximatel-y 16, H02p0und's of'waterzzpenhourem marwsepa'rator' IZ throughathe conduit. [3: to! the.

augment nozzle "01' jet: :5! 41 1and YlihBI'IC'BFiI'llJOIZbhQ secondary =separ-ator 22 while Lthe'i 8205 pounds, of water' is :discharge'd downwardlyitlrough the; oon'dfiit' l to the: lowerrheader l 8. :1 As; the hem perati re 'of the water passing downwardly through ithe" conduit f H 1 is approximately 6.0.5 B; and would flash "intosteam," approximately 3590 pounds of water-per -hour at :2.1"2":F. .ii-sadirected from" thexeconomizerdfi sthrough' the CODdUi'EPQ Q to be m'ixed With-thecwater passingifrom' t separator IZ'if-through the ccnduit lsLithusproe viding approximately1x800 pounds 'per z hour of water at approximately- 2500?" f. forpassage through th secondarylheating sectionrizl'. g'IThe. resultant. cliargeel fro'm the ssecondary: t'heating zsection l2 I into the-secondary"separatorifl with :5 0.-%;st ,eam quality, I and-the; pressureflwithin; thiszseparatciri-s approximately 11500trp. from e "secondary'vseparator through 117118;! c.on-- do which leadsreitherrto:a pointcof useor to a superheater'S M and tliencet to :az-pointxof usethrough iitl-i'e condui t .26. Approximately :-5'90fl of water perhour is directed from the. seoondaryaseparator F2 2 into:r the-natural icircu'lai-i tion section "I di to. be =heatedizand converted-into steam-within i the" tubes 5'29 o'f'the auxiliary heat ine'se'ction fl;

YIhe npressure drop: -:between the primary Separraitor' kl andtthe ::second'ary"- separator 12.2 is ape proximately 100 13.55. i., "including orifices-at the; tube iinl-et's ITherexmust. also be van equal; pressurmdropr the :c'onduit: t3: between the primary separator and "the secondary-separator; 2%.. This rdrop L in tpressu're can be: substantially 11301517 trolled-:-:by imeansr ft the valve-1 IT and the ads mentmozzleorrietw l4. The "auementnQzzleor jet ttbwadapted to utilize: approximatelyrhalf of thetzzpressure rdrop- :between "the" primary and secondary separators; to, 1 increase the circulation through "the natural circulation --.sec;tion 46., It should: also he noted that-z-th'e? natural: circulation section *I 6" 'shoiil'd" be-tprop'erly located to :absorb approximately :25 ioizthex total: heat absorbed the heatingisectionsilft and Z'l'and l6..

' vl hile T13 onezform', H118 obvious to those skilled I the art; that" i t is not 'so l-limited"but: is susceptible of various c'hange's and'rmodifications without depart.

ing from theespi rit and' scope of $13.9 claimed: in'

ventio'n. r

' I'claim as; my invention 2 'In' a forced circulationi.oncei ithrough i boiler,

apprimaryrheati-ng' sectiong-m'ean-s operable tordi! j rectly an'd continuously supply feed water:

ture fioffisteam and "-water :is .dis-

:Steam "isxdischarged the pressure, drop between said-primary sepia-'- 6 pressure tcs'ssaid. primailfy aitin ,.iffiQtiQHJifl 12.11- maryrseparator to receive steam and water I rater andsaid; se'condar .paraton azagIn; a. forced circu non one-thrcu'e' iboiien a pri ary h ating sec .nrmeans operable-tom:

rectly and ooritinuously sunplr reed;water unde maryfsenaratorzto receivesteamand-water "om said; primary-heatin "section, 1 a water no is duit. leading. from; said primary separatoni-asecondary beatings: section connected to'said W ter-ocnduit t'qsroflive water under pressure! fITOIllfiMd-gsllfi mam-separator, aseocnda'ry separator to receive steam; and;- water from said secondarrhfifli section, a natural: circulation "type. heating sec: ti'onhaving inlet andout-Iet conduits connected to, said-secondary separator, a -steamconduit leading: irom said; primary separator to the 0 1i let; conduit of saidnatural: circulat.ion type; heat;- ingxsection; and meansztd-vary the pressure drop through said steamwonduit; respjcnsive to :v ria tions. in water level within "said primary xsepae r-at'or. i v "3'. In forcedtirculationonceathrough boiler. aprimary heating sectiomneans operable to di rectiy'and 'ccntinuously sun-ply ieedwa erunder pressure to said primary:heatingsectiomxa ;pith. maryseparator to receive stea; and; water from said primary :heating section, a "wafer conduit leading' from saidprimaryseparatona secondary heatineseci/ion connected- .tov'said Water, conduit to receive, Water under pressure. from. said 'primarywseparator, a secondary separator to re ceive, steam. and water from said secondary "heating section, a natural :circulation type I heatineseo open :or closed positionsresponsive: to;variations.

in waterlevel within-said primary separation 4. In a-forced circulationwonce through boiler,- aprimam neatingseetion;means'operable, to directiyand; continuously-supply feedwater-under pressureto: said primary heatingrsectiom; a priemary separator to. receivesteam -andswater from said :prinmary heating section, a water *conduit leadingfrom saidxprimaryseparator rasecondary heating. section connected "to water conduit. to re'ceive waterouder pressure from said primary separator, a secondary vseparator "to inventi'on has beenz shorzn 'in but.

receive .isteam tandwaterfrom said secondary heatingseetion, zf'ar natural circulation atypeih'eata ing section having inlet "and outlet condutszconnee-ted to :said; secondary separator; and fa m-Ivec'ontrolled steam conduit leading from; said '.-p.1'-i mary se-parator to theloiitlet condiiitof.:said'natural'icircuiatiorrtsrpe'heatingsections f5. inf-alforced circulation once-through boilera primary heating section-,1:meansroperablent di rectlw and continuously; supply feed: water :umier pressure torsaidcprimary .lieatingisecti'on; aipri-r mary tseparatorato receireist'eamrand Wat rtro l;

said: lprimaryuheatingg sections-a we ,ricondwzt' said primary heating section, a water conduit leading from said primary separator, a, secondary heating-section connected to said water conduit to receive water under pressure from said primary separator, a secondary separator to receive steam and Water from said secondary heating section, a natural circulation type heating section having inlet and outlet conduits connected to said secondary separator, a valve controlled steam conduit leading from'said primary separator to the outlet conduit of said natural circulation type heating section, and an augment nozzle provided in the outlet conduit of said natural circulation type heating section to receive steam from said steam conduit.

6. In a forced circulation once-through boiler, a primary heating section, means operable to directly and continuously supply feed water under pressure to said primary heating section, a primary separator to receive steam and Water from said primary heating section, a water conduit leading from said primary separator, a secondary heating section connected to said water conduit to receive water under pressure from said primary separator, a secondary separator to receive steam and water from said secondary heating section, a natural circulation type heating section having inlet and outlet conduits connected to said secondary separator, a valve controlled steam conduit leading from said primary separator to the outlet conduit of said natural circulation type heating section, an augment nozzle provided in the outlet conduit of said natural circulation type heating section to receive steam from said steam conduit, and means to supply relatively cool feed water under pressure to said secondary heating section.

7. In a forced circulation once-through boiler, a primary heating section, means operable to directly and continuously supply feed water under pressure to said primary heating section, a primary separator to receive steam and Water from said primary heating section, a water conduit leading from said primary separator, a secondary heating section connected to said Water conduit to receive water under pressure fromsaid primary separator, a secondary separator to receive steam and water from said secondary heating section, a natural circulation type heating sectionhaving inlet and outlet conduits connected to said sec-ondary separator, a valve controlled steam conduit leading from said primary-separator to the outlet conduit of said natural circulation type heating section, an augment nozzle provided in the outlet conduit of said natural circulation type heating section to receive steam from said steam conduit, means to supply relatively cool feed water under pressure to said secondary heating section, a water return conduit leading down from each separator to the feed water inlet end of its respective heating section, and a check valve interposed in each of said water return conduits.

8. In a forced circulation once-through boiler, a, primary heating section, means operable to directly and continuously supply feed water under pressure to said primary heating section, a primary'separator to receive steam and water from said primary heating section, a, water conduit leading from said primary separator, a secondary heating section connected to said water conduit to receive water under pressure from said primary separator, a secondary separator to'receive steam and water from said secondary heating section, a natural circulation type heating secsaid secondary separator, a steam conduit leading from said primary separator to the outlet conduit of said natural circulation type heating section, means to vary the flow of steam through said steam conduit responsive to variations in water level within said primary separator, and an augment nozzle provided at the juncture of said steam conduit and the outlet conduit of said natural circulation type heating section.

9. In a forced circulation once-through boiler, 21. primary'heating section, means operable to directly and continuously'supply feed water under pressure to said primary heating section, a primary separator to receive steam and water from said primary heating section, a water conduit leading from said primary separator, a secondary heating section connected to said water conduit to receive water under pressure from said primary separator, a secondary separator to receive steam and water from said secondary heating section, a natural circulation type heating section having inlet and outlet conduits connected to said secondary separator, a steam conduit leading from said primary separator to the outlet conduit of said natural circulation type heating section, means to vary the flow of steam through said steam conduit responsive to varia-,

tions in water level Within said primary separator, an augment nozzle provided at the juncture of said steam conduit and the outlet conduit of said natural circulation type heating section, and means to supply relatively cool feed water under pressure to said secondary heating section.

10. In a forced circulation once-throughboiler, a primary'heating section, means operable to directly and continuously supply feed water under pressure to said primary heating section, a primary separator to receive steam and water from said primary heating section, a water conduit leading from said primary separator, a secondary heating section connected to said water conduit;

to receive Water under pressure from said primary separator, a secondary separator to receive steam and water from said secondary heating section, a natural circulation type heating section having inlet and outlet conduits connected to said secondary separator, a steam conduit leading from said primary separator to the outlet conduit of said natural circulation type heating section, means to vary the flow of steam through said steam conduit responsive to variations in water level within said primary separator, an augment nozzle provided at the juncture of said steam conduit and the outlet conduit of said natural circulation type heating section, means to supply relatively cool feed water under pressure to said secondary heating section, a water return conduit leading down from each separator to the feed water inlet end of its respective heating section, and a check valve interposed in each of said water return conduits.

11. In a forced circulation boiler, a primary heating section interconnected with a primary separator, a secondary heating section interconnected with a secondary separator, and a natural circulation type heating section having inlet and outlet conduits, an augment nozzle to supply steam from said primary separator to said inlet conduit and means to vary the pressure drop between said primary and secondary separators, said means controlling steam flow in said nozzle.

12. In a forced circulation boiler, a primary heating section interconnected with a, primary separator, a secondary heating section intercom;

i let.

nected with a secondary separator, and a natural circulation type heating section having inlet and outlet conduits, an augment nozzle to supply steam from said primary separator to said inlet conduit and means responsive to variations in water level in said primary separator, to vary the pressure drop between said primary and secondary separators, said means controlling steam flow in said nozzle.

13. In a forced circulation boiler, a primary heating section interconnected with a primary separator, a secondary heating section interconnected with a secondary separator, said primary separator having a steam line to said secondary heating section, and a natural circulation type heating section having inlet and outlet conduits, an augment nozzle to supply steam from said primary separator to said inlet conduit and means in said steam line responsive to variations in water level in said primary separator to vary the pressure drop between said primary and secondary separators, said means controlling steam fiow to said nozzle and said means controlling fluid flow through said primary separator out- JAMES W. HOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,703,228 French Feb. 26, 1929 1,860,363 La Mont May 31, 1932 1,907,845 Macrae et al. May 9, 1933 1,924,907 Bower Aug. 29, 1933 2,065,285 Miller Dec. 22, 1936 2,065,782 -Wo od' Dec. 29, 1936 2,078,479 Briggs 1- Apr. 27, 1937 2,177,917 Toensfeldt et a1. Oct. 31, 1939 2,294,501 Junkins Sept. 1, 1942 2,296,969 Wittmann Sept. 29, 1942 2,321,390 Juzi June 8, 1943 2,394,885 Baak Feb. 12, 1946 2,438,719 Saco, Jr., et a1 Mar. 30, 1948 FOREIGN PATENTS Number Country Date 848,060 France July 17, 1939 

